Has she ever gone broody? How old is she? Typically, but not always, they don’t go broody less than a year old.
The hatching behavior has largely been bred out of modern chickens. I have a broody that sets 1 or 2 times per year. About the time she’s due, I hold eggs back and place on the counter. I track them and put any older than 8-10 days in the refrigerator for consumption, rotating in fresh ones for ‘the day’ she goes broody. Don’t wash them. Don’t keep dirty eggs.
When she goes broody and sets on eggs in the box overnight a couple nights, take all the eggs out from under her and replace with the ones you kept on the counter. Mark them with sharpie just in case another lays in the same nest while she is setting.
To tell if the egg is fertilized, crack the ones you are going to eat, and look at the white spot. If the white spot is solid, it’s not fertile. If the white spot creates a bullseye, it’s fertile. All of the eggs layed around the time that egg was layed should be fertile also. When your chicken goes broody, at day 10-12 or so, you candle the eggs and remove the ones that aren’t developing.